Data storage systems are used to store large amounts of information received from one or more sources. A data storage system often comprises a storage controller in communication with one or more clients, often referred to as “hosts,” and also in communication with a plurality of data storage devices. A host computing device may send a storage controller a write command to write certain information to a data storage medium, and/or a read command to read information from a data storage medium, and/or a copy command to copy information from one data storage medium to another data storage medium. Host computers may also provide commands to a storage controller to establish or revise physical and/or logical configurations. In certain embodiments, a read command, or a write command, or a copy command, or a configuration command comprises a plurality of objects packaged in one command
In a multi-tier storage system a single storage system may include a number of different tiers, each containing storage devices having different performance characteristics. A higher performance tier of a particular storage system may include a number of solid state disks (SSDs) that provide short seek times. Because SSDs can be relatively expensive, the storage system may also include a lower performance tier made up of a number of slower devices, such as Serial Advanced Technology Attachment (SATA) drives. Although the SATA drives provide lower seek times, they can be a more inexpensive way to store data than additional SSD drives.
Because the higher performance tier may provide faster seek times, it may seem preferable to configure the storage system so that the higher performance tier is fully loaded to ensure that the high-performance tier is fully utilized. Unfortunately, although the storage devices in the higher performance tier have better performance in normal conditions, the performance of those storage devices is severely degraded when the devices are overloaded. In fact, when overloaded, the performance of those devices may be worse than that of the storage devices populating the lower performance tiers. As such, it can be difficult for a storage system to move an appropriate workload to the high performance devices of high performance tiers to ensure optimized performance of the storage system.